The present invention relates generally to the field of chemical compounds for medical treatments. More specifically, the present invention relates to compounds and devices for treating diseases or disorders associated with tissue damage due to environmental, interventional or autogenous injury.
Diseases and disorders induced by tissue damage are a growing concern in the healthcare industry. Typically, these diseases are characterized by prolonged or unwanted response to injury, including inflammation of a tissue portion, secretion of degrading enzymes and/or compounds resulting in tissue destruction within the region and attempted tissue repair. Examples of such conditions include proliferative and/or inflammatory disorders, for example, restenosis, psoriasis, graft rejection, arthritis and multiple sclerosis.
Psoriasis is an inflammatory skin disease characterized by raised scaly lesions. Specifically, skin cells are pushed to the skin surface more quickly than the skin surface can shed dead skin cells. The end result is the formation of scaly lesions which are invaded by macrophage, lymphocytes and neutrophils, creating inflammation and soreness of the tissue region. In addition, these cells may produce growth factors which may in fact cause skin cells to be produced even more rapidly, thereby worsening the condition. While the exact cause is unknown, psoriasis is hypothesized to be an autoimmune disorder.
Multiple sclerosis is an inflammatory disease that affects the nervous system of an individual. Typically, the disease causes demyelination in the brain which in turn leads to a progressive loss of motor functions. While the cellular mechanism triggering destruction of the myelin is not understood, it is known that there is a localized increase in astrocyte proliferation and protease activity in afflicted regions. As with psoriasis, the exact cause of multiple sclerosis is unknown although it is also hypothesized to be an autoimmune disorder.
Inflammatory bowel disease includes a number of specific diseases which cause intestinal inflammation or ulceration. For example, in ulcerative colitis, an inflammatory reaction involving the colonic mucosa leads to ulcerations. Furthermore, repeated inflammatory responses lead to fibrosis and a subsequent shortening of the colon. Similarly, Crohn""s disease is characterized by chronic inflammation of all layers of the intestinal wall.
Polycystic kidney disease is characterized by the formation of multiple cysts throughout the kidneys which progressively cause compression and destruction of kidney parenchyma. The disease appears to be caused by proliferation of epithelial cells in tubule segments within the kidneys, which in turn lead to fluid accumulation and enlargement of the kidneys.
Rheumatoid arthritis is a chronic inflammatory disease which causes pain, swelling and destruction of joints and can also lead to organ damage. Specifically, the disease is characterized by infiltration of the synovial membrane with white blood cells and a thickening of the synovial membrane. There is subsequent tissue growth within the joints as well as the release of degrading enzymes and compounds associated with the inflammatory response which leads to progressive destruction of the cartilage tissue. It is of note that rheumatoid arthritis is also hypothesized to be an autoimmune disorder.
Asthma is characterized by recurring airway obstruction caused by inflammatory cell infiltration, smooth muscle cell proliferation and hypertrophy in the airway and mucus secretion into the airway lumen.
Graft rejection occurs when the grafted tissue is recognized as foreign by the host""s immune system. This rejection leads to inflammation and arteriosclerosis in the graft tissue and surrounding area.
Hypertrophic disease involves cell growth in the absence of increased cell number. This definition applies to a number of conditions associated with trauma, including hypertrophic gastropathy, hypertrophic burn scars, keloids, or post-operative hypertrophy affecting numerous tissues. For example, hypertension is an increase in smooth muscle cell volume within a blood vessel due to excessive pressure, lack of oxygen/nutrients or enhanced production of hypertrophy-inducing factors released as a result of trauma distinct from the site of action (for example, kidney disease). Also, hypertrophic cardiac disease (for example, congestive heart failure, hypertrophic cardiomyopathy, valve replacement surgery) results from an increase in cardiomyocyte volume as a result of hypoxia, surgical intervention or genetic defect. Cellular hypertrophy and inflammation occur in the region affected by the causative factor.
Cutaneous fibrosis is an integral component of a variety of human disorders including keloids, hypertrophic scars, and most notably, scleroderma. Each has its own etiology and unique clinical characteristics, but all involve the disregulation of connective tissue metabolism, in particular, the activation of dermal fibroblasts. Atrophic scars also occur secondary to surgery, trauma, and common conditions such as acne vulgaris and varicella. Hypertrophic scars and keloids occur as the result of an exaggerated wound healing response of the skin following injury. Keloids and hypertrophic scars are benign fibrous growths that occur after trauma or wounding of the skin which are frequently pruritic, painful and occasionally form strictures. Keloid and hypertrophic scarring develops as a result of a proliferation of dermal tissue following skin injury. These proliferative scars are characterized by increased collagen and glycosaminoglycan content, as well as increased collagen turnover. Excision only of hypertrophic scars and keloids results in 45-100% recurrence. The current objective is to decrease scar height and reduce the number of post-operative recurrences.
Vascular lesions that develop in autologous saphenous vein grafts (SVG) after transplantation into the aorto-coronary circulation or the peripheral vascular circulation share elements of smooth muscle migration, proliferation,and fibrous tissue deposition in common with nibrointimal proliferation, post-operative recurrences of the fibrovascular proliferations of pterygia and keloids.
Restenosis is caused by vascular stress or injury and leads to vessel wall thickening and loss of blood flow. These stresses may be, for example, mechanical, hypoxia, injury, shear-stress, pharmacological, infectious, inflammatory, oxidative, immunogenic, diabetic or pressure. The normal arterial vessel wall consists of a regular arrangement of endothelial, smooth muscle and fibroblast cells, present in three distinct layers of endothelium, media and adventitia. A single layer of endothelial cells forms the luminal barrier to blood-borne signals that modulate vascular function. The adventitia, which forms the outer layer around the artery, consists primarily of extracellular matrix as well as some fibroblasts, nerve fibres and microvessels. The media consists of numerous layers of smooth muscle cells (SMCs) intermixed with extracellular matrix that is bound by the internal and external elastic lamina.
The response to injury or other stress stimuli varies between the different cellular components of the vessel. Endothelial cells are capable of proliferation and migration, properties that permit re-endothelialization of the vessel after denudation or injury (Reidy, 1985, Lab Invest 53: 513-520). Medial SMCs are also able to reversibly modulate their phenotype which allows for their proliferation and/or migration into the intima at the site of injury (Schwartz et al, 1995, Circ Res 77: 445-465). It is these characteristics that lead to the adaptive and pathogenic growth of SMCs which is key to vascular remodelling and lesion formation.
This is of particular concern for the treatment of coronary disease, wherein a common treatment for constricted, clogged or narrowed coronary arteries is balloon angioplasty. Angioplasty involves the use of a balloon-tipped catheter which is inserted into the heart""s vessels to open partially blocked, or stenotic, coronary arteries. While balloon angioplasty does widen the restricted artery, a significant number of patients have renewed narrowing of the widened segment soon after the procedure. This subsequent narrowing of the artery is called restenosis and can necessitate the repetition of the angioplasty procedure or require alternative treatment such as coronary bypass graft surgery. Furthermore, restenosis occurs as a result of trauma to the vessel regardless of the method by which the injury is inflicted. Therefore, restenosis is not exclusive to angioplasty and is a common result of other (cardiac or peripheral) revascularization procedures (eg. stenting) or procedures involving vascular grafting (eg. bypass surgery, organ transplantation). It is also a problem associated with hemoaccess and other procedures involving long term intravenous delivery.
Restenosis appears to be a response to injury of arterial wall, and appears to consist of the following events: platelet adhesion and aggregation on the damaged endothelium; release of platelet-derived growth factors; inflammation of the injured zone (Kornowski et al, 1998, J Am Coll Cardiaol 31: 224-230); secretion of specification chemotactic proteins from the damaged cells leading to recruitment of monocytes to the site of injury (Furukawa et al, 1999, Circ Res 84: 306-314); differentiation of monocytes into macrophages that produce matrix metalloproteinases required for cell migration; dedifferentiation of the smooth muscle cells after their activation by the growth factors; migration and proliferation of transformed smooth muscle cells, with secretion of extracellular matrix material; and re-growth of endothelium over the injured area.
U.S. Pat. No. 5,527,532 and 5,455,039 teach methods of regulating repair following injury to the lumen. In these patents, a modulator of cell or tissue growth, for example, heparin, is applied to an extraluminal site adjacent the injured tissue in a polymer release matrix such that the heparin is administered over a prolonged period. Other examples of growth modulating agents provided are angiotensin converting enzyme inhibitors, angiotensin, angiogenic growth factors, heparin binding growth factors, FGF, PDGF, TGF-xcex2, immunosuppressants, calcium channel inhibitor, cytokines and interleukins. The polymer release matrix is preferably composed of ethylene-vinyl acetate copolymer although other polyorthoester systems are also described.
There have been several proposed treatments for preventing restenosis, such as treatment with antioxidants or placing collapsible supports (i.e. stents) inside arteries, with varying success. As a consequence, there is an on-going search for compounds useful in treating proliferative disorders. For example, preliminary studies with 3-aminobenzamide, a potent (Ki=10 xcexcm) inhibitor of poly(ADP-ribose) polymerase (PARP), indicated this compound could inhibit cell growth at concentrations of 1 mM and greater (Zahradka and Yau, 1994).
It is important to note however that restenosis involves a number of distinct processes, including cell proliferation, cell migration and alterations in differentiated state (i.e. phenotype) of the medial smooth muscle cells, any of which could be a target for preventing restenosis. A major controversy still rages with respect to the relative importance of each process. It has become evident, however, that the rate of cell proliferation is infrequent in vessels undergoing restenosis (O""Brien et al, 1993, Circ Res 73: 223-231). Nevertheless, some inhibitors of cell proliferation have been shown to inhibit restenosis (Braun-Dullaeus et al, 1998, Circulation 98: 82-89). This discrepancy may be attributed to the effect of antiproliferative compounds on the other processes. For example, it has been demonstrated that the retinoblastoma protein regulates both the proliferation and the differentiation of skeletal muscles (Gu et al, 1993, Cell 72: 309-324), and a similar role in smooth muscle cells has been proposed (Pappas et al, 1998, J Surg Res 76: 149153). Similarly, a process necessary for proliferation may also be important for stimulating cell migration. For example, the transcription factor NF-xcexaKB has been shown to mediate events associated with both cell migration and cell proliferation (Lindner, 1998, Pathobiology 66: 311-320; Autieri et al, 1995, Biochem Biophys Res Commun 213: 827-836). Other intracellular factors also have dual functions. The role of cell migration has therefore become a focus of interest (Schwartz, 1997, J Clin Invest 99: 2814-2817; Casscells, 1992, Circulation 86: 723-729). Two lines of evidence suggest that migration has a greater contribution to restenosis than proliferation. One study (Bauriedel et al, 1992, Circulation 85: 554-564) suggests the smooth muscle cells of restenotic lesions migrate faster than their normal counterparts. Another study (Le Feuvre et al, 1998, CorArtery Dis 9: 805-814) showed that remodelling of the vessel after angioplasty occurred with minimal proliferation. Furthermore, this report suggests the majority of proliferating cells were not of smooth muscle origin. These observations support the results reported in several other studies relating to migration versus proliferation. First, inhibition of matrix metalloproteinases, the enzymes responsible for degrading the extracellular matrix and therefore freeing the cells for migration, prevents inhibit restenosis (George et al, 1998, Hum Gene Ther 9: 867-877). These agents do not inhibit cell proliferation. Similarly, the kinase inhibitor fasudil has been shown to reduce restenosis while lacking anti-proliferation activity (Negoro et al, 1999, Biochem Biophys Res Comm 262: 211-215). Second, various agents have been demonstrated to inhibit smooth muscle cell proliferation without having any effect in blocking restenosis. Among these compounds are lovastatin and fluvastin (two of several HMG-COA reductase inhibitors), enalapril (a typical ACE inhibitor), colchicine, carvedilol, heparin and phosporothioate oligonucleotides (Freed et al, 1995, Am J Cardiol 76: 1185-1188; Geary et al, 1995, Circulation 91: 2972-2981; Serruys et al, 2000, Circulation 101: 1512-1518; Gradus-Pizio, 1995, J Am Coll Cardiol 6: 15491-1557; Simon et al, 1999, Antisense Nuci Acid Drug Dev 9: 549-553). It must also be stressed that arterial remodelling during restenosis does not require cell proliferation (Le Feuvre et al, 1998).
These data therefore support the premise that modulation of smooth muscle phenotype, exclusive of the change in proliferative potential of these cells, is the most important facet for therapeutic intervention. It is nevertheless unclear what component of the change is most important. Migration is considered to be essential. However, the deposition of extracellular matrix proteins is integral to formation of the neointima. Infiltration by inflammatory cells contributes as well. Thus, approaches directly focused upon inhibiting cell proliferation may not be successful.
As discussed above, a major emphasis for the treatment of restenosis has been placed on the prevention of either cell proliferation or migration. Alternatively, the aim has been to prevent inflammation. When one examines the etiology of restenosis, which results from an exaggerated wound healing process, a number of distinct responses are evident such as, for example, proliferation, migration, inflammation and fibrosis. In all cases, these events occur as a result of phenotypic reprogramming of the smooth muscle cells. For instance, the release of metalloproteinases that degrade the extracellular matrix permits migration. Migration into the vascular lumen allows proliferation. The cells also synthesize and secrete abundant collagen and fibronectin once they enter the lumen. Inflammation due to invasion by monocytes and leukocytes results from the expression of specific adhesion molecules that direct infiltration. Their entry is also enhanced by the secretion of specific chemattractant molecules. All of these events result from modulation of smooth muscle cell phenotype due to trauma or stress. Inhibition of the differentiation process would therefore accomplish all of the relevant objectives since each event would be blocked as well. As such, an anti-differentiation agent would likely be an effective treatment for the diseases and disorders induced by tissue damage discussed above.
ADP-ribosylation is a post-translational modification comprising the attachment of ADP-ribose to proteins (shown in FIG. 16), either as single moieties or as a long polymer (Zahradka and Yau, 1994, Mol Cell Biol 138: 91-98). ADP-ribosylation occurs in two distinct forms: nuclear poly(ADP-ribosyl)ation and mono(ADP-ribosyl)ation (Moss and Zahradka in ADP-ribosylation: Metabolic Effects and Regulatory Functions (Boston: Kluwer Academic Publishers, 1994)). Nuclear poly(ADP-ribosyl)ation regulates protein-DNA interactions (Zahradka and Ebisuzaki, 1982, Eur J Biochem 127: 579-585) and is proposed to be involved in for example the modulation of chromatin condensation via histone modification (de Murcia et al, 1986, J Biol Chem 261: 7011-7017) and the regulation of DNA repair activity following damage by alkylating agents and high energy irradiation (Lindahl et al, 1995, TIBS 20: 405-411). In addition, proteolytic cleavage of poly(ADP-ribose) polymerase (PARP) has also been recently identified as one of the earliest events in apoptosis, or programmed cell death (Duriez and Shah, 1997, Biochem Cel Biol 75: 337-349). Mono(ADP-ribosyl)ation, on the other hand, is a process associated primarily with the cytoplasmic and membrane fractions of a cell. The best understood of the mono(AD-Pribosyl)ation reactions are those of bacterial toxins. Several eukaryotic mono(ADP-ribosyl)ation transferases (ADPRTs), however, have also been identified and characterized. For example, cysteine-dependent ADPRT modifies G, while an arginine-dependent ADPRT modifies Gs (Tanuma et al, 1988, J Biol Chem 263: 5485-5489; Inageda et al, 1991, Biochem Biophys Res Commun 176: 1014-1019). As well, a phosphatidylinositol-linked arginine-dependent ADPRT is present on the external surface of skeletal and cardiac cells, and controls cell attachment by modifying xcex17-integrin (Okazaki and Moss, 1998, J Biol Chem 273: 23617-23620). Other ADPRTs are associated with vesicular movement in the Golgi, since ARFs (ADP-ribosylation factors) are essential for these events (Kanoh et al, 1997, J Biol Chem 272: 5421-5429). ADPRTs have also been linked to the activation of small GTP-binding proteins such as ras, rho and raf, key components in signal transduction (Maehama et al, 1994, Mol Cell Biochem 138: 135-140). The ubiquitous presence of ADPRTs in all cell types suggests that they are crucial elements in normal cell function.
As stated above, preliminary studies with 3-aminobenzamide, a potent (K1=10 xcexcM) inhibitor of PARP, indicated this compound could inhibit cell growth at concentrations of 1 mM and greater (Zahradka and Yau, 1994). These observations, as well as the findings reported by other laboratories, did not fit the pattern expected for PARP. Specifically, while there was considerable evidence to link PARP with DNA recombination events and DNA repair (Lindahl et al, 1995, Philos Trans R Soc Lond B Biol Sci 347: 57-62), there was only limited evidence to link PARP directly with cell proliferation. The studies by Rankin et al (Rankin et al, 1989, J Biol Chem 264: 4312-4317) and Banasik et al (Banasik et al, 1992, J Biol Chem 267: 1569-1575) clearly showed that 3-aminobenzamide inhibited mono(ADP-ribosyl)ation at high concentrations ( greater than 1 mM). Based on these observations, it was postulated that inhibition of mono(ADP-ribosyl)ation was the mechanism by which 3-aminobenzamide inhibited cell growth (Zahradka and Yau, 1994; Yau et al, 1998, Eur J Biochem 253: 91-100).
As a consequence, decoy substrates of mono(ADP-ribosyl)ation were sought to be tested as anti-inductive agents. Meta-iodobenzylguanidine (MIBG) is a norepinephrine analogue that also belongs to a class of compounds distinguished by a guanidino moiety. MIBG has also been shown to be a selective inhibitor of normal function of arginine-dependent mono(ADP-ribosyl)ation (Loesberg et al, 1990, Biochim Biophys Acta 1037: 92-99) and it is the guanidino group that is the functional portion with respect to modification by ADP-ribosylation.
It has also been shown that while MIBG apparently prevents an increase in cell number, it had no effect on DNA synthesis, based on thymidine uptake experiments (Thyberg et al, 1995, Differentiation 59: 243-252). On this basis, it was concluded that MIBG inhibits progression through the cell cycle, although no evidence for this mechanism was presented. Instead, there was commentary about the involvement of c-ras, a critical mediator of cell progression that may be a target for mono(ADP-ribosyl)ation. On the other hand, Thyberg et al observed that MIBG decreased the production of collagen type I, the most abundant component of the extracellular matrix. Similarly, there was a lesser conversion of the cells to the dedifferentiated (synthetic) state in the presence of MIBG. It is argued that MIBG may therefore affect the interaction of smooth muscle cells with the extracellular matrix and that in view of this, MIBG may be a tool for investigating the role of smooth muscle cells in connection with atherogenesis and restenosis. However, it is important to note that Thyberg does not teach or suggest the use of MIBG as a treatment for restenosis.
MIBG has previously been shown to be selectively accumulated in adrenal glands following injection into dogs (Wieland et al, 1981, J Nucl Med 22: 22-31). This study was based on observations that aralkylguanidines are potent neuron blocking agents that apparently act on adrenergic nerves (Short and Darby, 1967, J Med Chem 10: 833-840). Since that time, MIBG has been used as an imaging agent for the detection of pheochromocytoma (tumors of the adrenal gland) via scintillography (Hoefnagel et al, 1987, Eur J Nucl Med 13: 187-191). It is of note that in these imaging experiments, MIBG combined with a label was used at a maximum concentration of approximately 0.065 mg/kg of the test subject. As such, MIBG itself was used as a carrier for delivering radiation doses and not as an actual treatment. Its application to other neuroendocrine tumors, particularly neuroblastomas, has also been tested, and it has been found to be an extremely sensitive diagnostic tool. Other carcinomas are also detected with MIBG, but other imaging agents have been shown to provide greater sensitivity. Radiolabelled MIBG is employed in scintillography, however, the amounts that are utilized are quite small and pose no danger to the patient or the organ. Trials with MIBG as a radiopharmaceutical agent have been designed on the basis that accumulation of high doses of radioactivity can inhibit tumor growth (Shapiro et al, 1995, Q J Nucl Med 39: 55-57). Thus higher doses of radiolabelled MIBG may be useful in treatment. To date, there have been encouraging results, but insufficient to support first line use (Taal et al, 1996, J Clin Oncol 14:1829-1836). Nevertheless, it has been found useful for treating inoperable tumors. Furthermore, there is evidence that it may be more effective when combined with other therapies. However, it is important to note that MIBG was selected based on its accumulation in fast-growing cells and not on its activity as an ADPRT inhibitor.
Furthermore, MIBG""s accumulation in sympathetic neurons led to tests for its utility in identifying changes in cardiac function. This reasoning was based on the fact that cardiac innervation is altered in the hypertrophied heart. In part this is considered a result of sympathetic neuron loss after myocardial infarction. Thus a reduction in MIBG uptake by cardiac tissues, called an MIBG defect, is deemed to correlate with cardiac disfunction (Somsen et al, 1996, Int J Card Imaging 12: 305-310; Tamaki et al, 1997, Ann Nucl Med 11: 55-66). No clear consensus on the utility of MIBG in the diagnosis of heart failure has yet been reached, although there are still numerous attempts to identify the conditions for which MIBG may be useful. However, it is once again the uptake characteristics of MIBG that are being utilized.
In other studies, MIBG has been used as an anti-cancer drug at a concentration of approximately 1.5 mg/kg of subject (Kuin et al, 1998, Cancer Chemother Pharmacol 42: 37-45; Kuin et al, 1999, Brit J Cancer 79: 793-801). However, it is important to note that in these studies, MIBG and BG were selected based on its activity as a mitochondrial inhibitor. Furthermore, the MIBG analogue MIBA is also a mitochondrial inhibitor and would also have been suitable.
Clearly, there is a need for improved treatments and methods for preventing disorders that occur as a result of alterations in the migratory, proliferative and inflammatory responses of cells within tissues. In particular, the treatments should prevent the shift into the inductive state and the cell phenotype modification associated with tissue repair. Ideally, these treatments should be designed to target the area at risk preferentially or to be localized thereabouts. In this manner, potential side effects and/or complications from treatment could be minimized.
According to a first aspect of the invention, there is provided a pharmaceutical composition for treating or preventing an injury-related disorder comprising an ADPRT decoy substrate and a suitable excipient.
According to a second aspect of the invention, there is provided an ADPRT decoy substrate for treating or preventing an injury-related disorder.
According to a third aspect of the invention, there is provided a method of treating or preventing an injury-related disorder comprising: providing a pharmacologically effective amount of a pharmaceutical composition comprising an ADPRT decoy substrate and a suitable excipient; and administering the pharmaceutical composition to an individual inflicted with the injury-related disorder.
According to a fourth aspect of the invention, there is provided a method of inhibiting restenosis comprising: providing a pharmaceutical composition comprising an ADPRT decoy substrate in admixture with an adhesive agent; providing a damaged vessel; and applying the pharmaceutical composition to the damaged vessel, thereby inhibiting smooth muscle cell differentiation, migration and proliferation.
According to a fifth aspect of the invention, there is provided a kit comprising an ADPRT decoy substrate for treating or preventing an injury-related disorder and instructions for utilizing the ADPRT decoy substrate for treating or preventing the injury related disorder.